The present invention relates to a method for imparting controlled release characteristics to a plastic or paper substrate resulting from the UV cure of a UV curable epoxysilicone composition. More particularly, the present invention relates to the use of UV curable epoxysilicone compositions having a particular amount of a control release additive, such as a C.sub.(8-16) alkylphenol, or an alkylphenol substituted disiloxane incorporated therein.
Prior to the present invention, silicone release coatings were widely used to render various surfaces non-adherent. Non-adherent silicone treated paper is often used to support labels contacting a pressure-sensitive adhesive (PSA) prior to the use of such labels. In addition, non-adherent surfaces are often necessary in industrial packaging.
Silicones have been widely recognized for their value as release coatings particularly with respect to their use with PSAs. The release coating industry is also searching for ways to synthesize release coating compositions which can be converted to cured release coatings having a predictable variation in release characteristics when contacted with PSAs, referred to hereinafter as "controlled or differential release".
Certain coating compositions utilizing epoxy or acrylic functional groups as modifiers of the release properties of cured silicone resins are taught by U.S. Pat. No. 4,576,999. UV cured epoxysilicone polymers having controlled release are discussed in copending application Ser. No. 171,498, filed Mar. 21, 1988, utilizing condensed organosiloxy units substituted with esterified benzoyl groups. Another method for modifying release characteristics of UV curable epoxy functional silicones is taught in U.S. Pat. No. 4,547,431, resulting from the addition of epoxy monomers.
Controlled or differential release of organopolysiloxane resins is also discussed in copending application Ser. No. 225,986, filed July 29, 1988. Organopolysiloxanes are modified with monovalent phenolic radicals having from 6 to 26 carbon atoms, monovalent acrylic organic radicals, or monovalent epoxy functional organic radicals. These modified silicones have been found to have controlled release. The incorporation of the phenolic groups onto the organopolysiloxane backbone is achieved by an SiH to vinyl addition reaction catalyzed by a platinum catalyst. Although effective controlled release results are achieved, it has been found that residual amounts of unreacted allylphenol used to incorporate phenolic groups into the resin, often impart an undesirable phenolic odor to the silicone release resin.